/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.cassandra;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;
import java.io.UnsupportedEncodingException;
import java.util.Locale;

import org.slf4j.ILoggerFactory;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import ch.qos.logback.classic.Level;
import ch.qos.logback.classic.LoggerContext;
import ch.qos.logback.classic.spi.LoggerContextListener;
import ch.qos.logback.core.status.Status;
import ch.qos.logback.core.status.StatusListener;
import org.apache.cassandra.config.CassandraRelevantProperties;
import org.apache.cassandra.distributed.shared.InstanceClassLoader;

import static org.apache.cassandra.config.CassandraRelevantProperties.SUN_STDERR_ENCODING;
import static org.apache.cassandra.config.CassandraRelevantProperties.SUN_STDOUT_ENCODING;

/*
 * Listen for logback readiness and then redirect stdout/stderr to logback
 */
public class LogbackStatusListener implements StatusListener, LoggerContextListener
{

    public static final PrintStream originalOut = System.out;
    public static final PrintStream originalErr = System.err;

    private volatile boolean hadPreInstallError = false;
    private volatile boolean haveInstalled = false;
    private volatile boolean haveRegisteredListener = false;

    private PrintStream replacementOut;
    private PrintStream replacementErr;

    @Override
    public void addStatusEvent(Status s)
    {
        if (!haveInstalled && (s.getLevel() != 0 || s.getEffectiveLevel() != 0))
        {
            // if we encounter an error during setup, we're not sure what state we're in, so we just don't switch
            // we should log this fact, though, so that we know that we're not necessarily capturing stdout
            LoggerFactory.getLogger(LogbackStatusListener.class)
                         .warn("Encountered non-info status in logger setup; aborting stdout capture: '" + s.getMessage() + '\'');
            hadPreInstallError = true;
        }

        if (hadPreInstallError)
            return;

        if (s.getMessage().startsWith("Registering current configuration as safe fallback point"))
        {
            onStart(null);
        }

        if (haveInstalled && !haveRegisteredListener)
        {
            // we register ourselves as a listener after the fact, because we enable ourselves before the LoggerFactory
            // is properly initialised, hence before it can accept any LoggerContextListener registrations
            tryRegisterListener();
        }

        if (s.getMessage().equals("Logback context being closed via shutdown hook"))
        {
            onStop(null);
        }
    }

    private static PrintStream wrapLogger(Logger logger, PrintStream original, CassandraRelevantProperties encodingProperty, boolean error) throws Exception
    {
        final String encoding = encodingProperty.getString();
        OutputStream os = new ToLoggerOutputStream(logger, encoding, error);
        return encoding != null ? new WrappedPrintStream(os, true, encoding, original)
                                : new WrappedPrintStream(os, true, original);
    }

    private static class ToLoggerOutputStream extends ByteArrayOutputStream
    {
        final Logger logger;
        final String encoding;
        final boolean error;

        private ToLoggerOutputStream(Logger logger, String encoding, boolean error)
        {
            this.logger = logger;
            this.encoding = encoding;
            this.error = error;
        }

        @Override
        public void flush() throws IOException
        {
            try
            {
                //Filter out stupid PrintStream empty flushes
                if (size() == 0) return;

                //Filter out newlines, log framework provides its own
                if (size() == 1)
                {
                    byte[] bytes = toByteArray();
                    if (bytes[0] == 0xA)
                        return;
                }

                String statement;
                if (encoding != null)
                    statement = new String(toByteArray(), encoding);
                else
                    statement = new String(toByteArray());

                if (error)
                    logger.error(statement);
                else
                    logger.info(statement);
            }
            finally
            {
                reset();
            }
        }
    };

    private static class WrappedPrintStream extends PrintStream
    {
        private long asyncAppenderThreadId = Long.MIN_VALUE;
        private final PrintStream original;

        public WrappedPrintStream(OutputStream out, boolean autoFlush, PrintStream original)
        {
            super(out, autoFlush);
            this.original = original;
        }

        public WrappedPrintStream(OutputStream out, boolean autoFlush, String encoding, PrintStream original) throws UnsupportedEncodingException
        {
            super(out, autoFlush, encoding);
            this.original = original;
        }

        /*
         * Long and the short of it is that we don't want to serve logback a fake System.out/err.
         * ConsoleAppender is replaced so it always goes to the real System.out/err, but logback itself
         * will at times try to log to System.out/err when it has issues.
         *
         * Now here is the problem. There is a deadlock if a thread logs to System.out, blocks on the async
         * appender queue, and the async appender thread tries to log to System.out directly as part of some
         * internal logback issue.
         *
         * So to prevent this we have to exhaustively check before locking in the PrintStream and forward
         * to real System.out/err if it is the async appender
         */
        private boolean isAsyncAppender()
        {
            //Set the thread id based on the name
            Thread currentThread = Thread.currentThread();
            long currentThreadId = currentThread.getId();
            if (asyncAppenderThreadId == Long.MIN_VALUE &&
                currentThread.getName().equals("AsyncAppender-Worker-ASYNC") &&
                !InstanceClassLoader.wasLoadedByAnInstanceClassLoader(currentThread.getClass()))
            {
                asyncAppenderThreadId = currentThreadId;
            }
            if (currentThreadId == asyncAppenderThreadId)
                original.println("Was in async appender");
            return currentThreadId == asyncAppenderThreadId;
        }

        @Override
        public void flush()
        {
            if (isAsyncAppender())
                original.flush();
            else
                super.flush();
        }

        @Override
        public void close()
        {
            if (isAsyncAppender())
                original.close();
            else
                super.flush();
        }

        @Override
        public void write(int b)
        {
            if (isAsyncAppender())
                original.write(b);
            else
                super.write(b);
        }

        @Override
        public void write(byte[] buf, int off, int len)
        {
            if (isAsyncAppender())
                original.write(buf, off, len);
            else
                super.write(buf, off, len);
        }

        @Override
        public void print(boolean b)
        {
            if (isAsyncAppender())
                original.print(b);
            else
                super.print(b);
        }

        @Override
        public void print(char c)
        {
            if (isAsyncAppender())
                original.print(c);
            else
                super.print(c);
        }

        @Override
        public void print(int i)
        {
            if (isAsyncAppender())
                original.print(i);
            else
                super.print(i);
        }

        @Override
        public void print(long l)
        {
            if (isAsyncAppender())
                original.print(l);
            else
                super.print(l);
        }

        @Override
        public void print(float f)
        {
            if (isAsyncAppender())
                original.print(f);
            else
                super.print(f);
        }

        @Override
        public void print(double d)
        {
            if (isAsyncAppender())
                original.print(d);
            else
                super.print(d);
        }

        @Override
        public void print(char[] s)
        {
            if(isAsyncAppender())
                original.println(s);
            else
                super.print(s);
        }

        @Override
        public void print(String s)
        {
            if (isAsyncAppender())
                original.print(s);
            else
                super.print(s);
        }

        @Override
        public void print(Object obj)
        {
            if (isAsyncAppender())
                original.print(obj);
            else
                super.print(obj);
        }

        @Override
        public void println()
        {
            if (isAsyncAppender())
                original.println();
            else
                super.println();
        }

        @Override
        public void println(boolean v)
        {
            if (isAsyncAppender())
                original.println(v);
            else
                super.println(v);
        }

        @Override
        public void println(char v)
        {
            if (isAsyncAppender())
                original.println(v);
            else
                super.println(v);
        }

        @Override
        public void println(int v)
        {
            if (isAsyncAppender())
                original.println(v);
            else
                super.println(v);
        }

        @Override
        public void println(long v)
        {
            if (isAsyncAppender())
                original.println(v);
            else
                super.println(v);
        }

        @Override
        public void println(float v)
        {
            if (isAsyncAppender())
                original.println(v);
            else
                super.println(v);
        }

        @Override
        public void println(double v)
        {
            if (isAsyncAppender())
                original.println(v);
            else
                super.println(v);
        }

        @Override
        public void println(char[] v)
        {
            if (isAsyncAppender())
                original.println(v);
            else
                super.println(v);
        }

        @Override
        public void println(String v)
        {
            if (isAsyncAppender())
                original.println(v);
            else
                super.println(v);
        }

        @Override
        public void println(Object v)
        {
            if (isAsyncAppender())
                original.println(v);
            else
                super.println(v);
        }

        @Override
        public PrintStream printf(String format, Object... args)
        {
            if (isAsyncAppender())
                return original.printf(format, args);
            else
                return super.printf(format, args);
        }

        @Override
        public PrintStream printf(Locale l, String format, Object... args)
        {
            if (isAsyncAppender())
                return original.printf(l, format, args);
            else
                return super.printf(l, format, args);
        }

        @Override
        public PrintStream format(String format, Object... args)
        {
            if (isAsyncAppender())
                return original.format(format, args);
            else
                return super.format(format, args);
        }

        @Override
        public PrintStream format(Locale l, String format, Object... args)
        {
            if (isAsyncAppender())
                return original.format(l, format, args);
            else
                return super.format(l, format, args);
        }

        @Override
        public PrintStream append(CharSequence csq)
        {
            if (isAsyncAppender())
                return original.append(csq);
            else
                return super.append(csq);
        }

        @Override
        public PrintStream append(CharSequence csq, int start, int end)
        {
            if (isAsyncAppender())
                return original.append(csq, start, end);
            else
                return super.append(csq, start, end);
        }

        @Override
        public PrintStream append(char c)
        {
            if (isAsyncAppender())
                return original.append(c);
            else
                return super.append(c);
        }    }

    public boolean isResetResistant()
    {
        return false;
    }

    public synchronized void onStart(LoggerContext loggerContext)
    {
        if (!hadPreInstallError && !haveInstalled)
        {
            if (InstanceClassLoader.wasLoadedByAnInstanceClassLoader(getClass())
                || System.out.getClass().getName().contains("LogbackStatusListener"))
            {
                // don't operate if we're a dtest node, or if we're not the first to swap System.out for some other reason
                hadPreInstallError = true;
                return;
            }
            try
            {
                Logger stdoutLogger = LoggerFactory.getLogger("stdout");
                Logger stderrLogger = LoggerFactory.getLogger("stderr");

                replacementOut = wrapLogger(stdoutLogger, originalOut, SUN_STDOUT_ENCODING, false);
                System.setOut(replacementOut);
                replacementErr = wrapLogger(stderrLogger, originalErr, SUN_STDERR_ENCODING, true);
                System.setErr(replacementErr);
            }
            catch (Exception e)
            {
                throw new RuntimeException(e);
            }
            haveInstalled = true;
        }
    }

    public synchronized void onReset(LoggerContext loggerContext)
    {
        onStop(loggerContext);
    }

    public synchronized void onStop(LoggerContext loggerContext)
    {
        if (haveInstalled)
        {
            if (replacementOut != null) replacementOut.flush();
            if (replacementErr != null) replacementErr.flush();
            System.setErr(originalErr);
            System.setOut(originalOut);
            hadPreInstallError = false;
            haveInstalled = false;
            haveRegisteredListener = false;
            if (haveRegisteredListener)
            {
                ((LoggerContext)LoggerFactory.getILoggerFactory()).removeListener(this);
            }
        }
    }

    public void onLevelChange(ch.qos.logback.classic.Logger logger, Level level)
    {
    }

    private synchronized void tryRegisterListener()
    {
        if (haveInstalled && !haveRegisteredListener)
        {
            ILoggerFactory factory = LoggerFactory.getILoggerFactory();
            if (factory instanceof LoggerContext)
            {
                ((LoggerContext) factory).addListener(this);
                haveRegisteredListener = true;
            }
        }
    }
}